Mastectomy patients may have significant psychologic-related problems. Breast reconstruction provides in these cases substantial benefits in restoring body image and health-related quality of live. Autologous free tissue transfer is the treatment of choice due to excellent outcome. The purpose of this study was to elucidate the effect of the risk factors on the microcirculation and clinical outcome.In this prospective study, 21 patients with a free transverse rectus abdominis (TRAM) flap breast reconstruction were included. Patient demographics and flap characteristics were recorded. Blood flow was recorded in the central part (zone I) and the distal part (zone IV) of the flap with the laser Doppler flowmetry (LDF; Perimed).In this study, increased flap complications were seen in smokers when compared with nonsmokers (P < 0.000). LDF was higher in the older patient population (P = 0.008) in zone IV. Smoking, especially in combination with a high flap weight (HFW), revealed lower blood-flow values (P = 0.020) in zone IV. Other possible influencing risk factors such as a HFW and history of radio- and chemotherapy did not alter the microcirculation. Patients with smoking and a HFW did also show decreased blood flow but also more severe flap complications.Smoking, especially in patients with a HFW, impairs the free TRAM flap microcirculation in zone IV. In our opinion, these patients can still be included for reconstruction. However, extra care has to be taken during flap design to minimize disturbed wound healing.